Major League Gaming was the biggest non-company-affiliated eSports gaming league, but due to a problem with Cataclysm compatibility with their spectating client at launch, MLG could not include World of Warcraft in its tournament circuit after the end of the 2010 season.[3]

Unfortunately due to mounting debts, MLG has basically been dissolved by Activision-Blizzard in a buyout at the end of 2015.[4]

So far Blizzard appears to have a low priority for spectating client compatibility support in-game.